# US 12,009,562 B2 · High solubility iron hexacyanides

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- Number: US 12,009,562 B2
- Document ID: US12009562B2
- Status: Granted
- Kind: B2
- Application number: 17/727,904
- Filed: 2022-04-25
- Published: 2022-08-11
- Granted: 2024-06-11
- Earliest claimed: 2012-08-15
- Assignees: Lockheed Martin Energy, LLC
- Applicants: Lockheed Martin Energy, LLC
- Inventors: Arthur J. Esswein; John Goeltz; Desiree Amadeo
- Web page: https://patentgrep.com/patent/US12009562B2

## CPC

- H01M 8/222: {Fuel cells in which the fuel is based on compounds containing nitrogen, e.g. hydrazine, ammonia}
- H01M 8/08: Fuel cells with aqueous electrolytes
- H01M 8/188: {by recharging of redox couples containing fluids; Redox flow type batteries}
- H01M 8/20: Indirect fuel cells, e.g. fuel cells with redox couple being irreversible (H01M8/18 takes precedence)
- H01M 2300/0002: Aqueous electrolytes
- Y02E 60/36: Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
- Y02E 60/50: Fuel cells
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

Stable solutions comprising high concentrations of charged coordination complexes, including iron hexacyanides are described, as are methods of preparing and using same in chemical energy storage systems, including flow battery systems. The use of these compositions allows energy storage densities at levels unavailable by other iron hexacyanide systems.

## Claims

### Claim 1

A method, comprising:
(a) reacting H4[Fe(CN)6] with one or more Na+ and K+-containing basic salts so as to produce an aqueous solution comprising both Na+ and K+ cations and having a concentration of Fe(CN)64− in the aqueous solution that exceeds a concentration of Fe(CN)64− in either a saturated aqueous solution of Na4[Fe(CN)6] or a saturated aqueous solution of K4[Fe(CN)6] in water at a same temperature as that of the aqueous solution,
the one or more Na+/K+-containing basic salts optionally comprising one or more of hydroxide, carbonate, or bicarbonate.

### Claim 2 (depends on 1)

The method of claim 1, wherein the one or more Na+/K+-containing basic salts comprise one or more of hydroxide, carbonate, or bicarbonate.

### Claim 3 (depends on 2)

The method of claim 2, wherein the one or more Na+/K+-containing basic salts comprise hydroxide.

### Claim 4 (depends on 2)

The method of claim 2, wherein the one or more Na+/K+-containing basic salts comprise one or more of carbonate or bicarbonate.